Forging lubricant and method of using same



Patented Mar. 11, 1952 UNITED STATS ATENT OFFICE FORGING LUBRICANT AND METHOD OF USING SAME No Drawing. Application March 15, 1945, Serial No. 583,004

13 Ciaims.

This invention relates to making forgings and pressings, especially those of aluminum and aluminum base alloys which contain more than 70 per cent aluminum. For convenience this class of metal products will be referred to as forged or pressed aluminous metal products.

In producing forgings and pressings, a hot slug or partially shaped article is squeezed between two dies. The term slug will be used below, however, to describe the metal article to be hot shaped in any given working operation. The pressure exerted on the slug causes the hot metal to flow over the face of the die and into any recesses provided therein. The pressure is applied for a very short period of time so that the metal of the slug must flow almost instantaneously to pro duce the desired shape of article. If the surface of both the die and slug are bare, they will tend to stick together and the friction between them will prevent proper filling of the die, and particu larly of the die recesses. These difficulties are generally overcome, to some extent, by coating the die with a substance, or a mixture of substances, which reduces the resistance to flow of metal over the die and minimizes the metal to metal contact, and are therefor designated as lubricants.

Flake graphite and similar solid lubricants mixed with water or an organic vehicle have been employed, and various organic oils and greases have also been proposed for the purpose. Such lubricants have been applied by spraying or swabbing them on the dies before each slug is forged or pressed. However, the use of such lubricating procedures has resulted in the production of large quantities of smoke, steam, and other vapors which are both annoying to the operators and necessitate making provision for their escape from the dies during the metal working operation, since at least part of the gaseous material is produced While the slug is being shaped between the dies. The escape of the vapors is facilitated by providing vents in the dies or at the parting line. Moreover, if oil or grease is employed in the lubricant, it usually carbonizes to some extent and leaves a tenacious film on the article which must be removed before transfer to the next manufacturing operation. An other disadvantage of lubricating dies, as has been described, is that a special operator may be required to apply the lubricant, or if an extra operator is not required, then one of the other operators must take time to do this, with a resultant loss in production of the forgings or press? mgs.

It is an object of our invention to provide a lubricating composition for forging or pressing operations which does not yield smoke or vapors, but yet reduces resistance to the flow of metal over the die surface, and to provide a method of applying the composition which can be conveniently employed without loss of time on the part of forge or press operators. Another object is to provide lubricant which will facilitate proper filling of the dies and whose residues remaining on the article can be easily removed. Still another object of the invention is to improve the filling of the dies by the metal being shaped therein.

We have discovered that by providing a hot' metal slug, prior to forging or pressing, with an adherent lubricating coating by coating the slug with a slurry containing a liquid vehicle, such as water, a lubricant, an organic adhesive, and a salt, and driving off the vehicle, hot worked articles can be produced without encountering the difi'iculties described above. The lubricant component employed should be one which is stable under the temperature conditions encountered in the hot shaping operation in the sense that the lubricant does not, to any marked extent, vaporize or form substances that do vaporize in the course of the shaping operation. Graphite is the lubricant preferred. Good results can also be obtained by using powdered mica or aluminum powder of the type customarily used in making aluminum paints as the lubricant. These three materials all resemble each other in respect to their initial flat, flake-like character, their substantial insolubility in water or other vehicle used in making the slurry, and in that in combination with other components of the slurry they tend to reduce the friction between the slug and die surfaces. These substances may be used separately or in combination in the composition of any given lubricant coating.

The adhesive component of the lubricant coating may be selected from a large group of materials. These materials should either be soluble in water or whatever vehicle is utilized or they should form colloids or suspensions. They must be capable of being uniformly distributed throughout the slurry and the dried lubricant coating on the slug. Organic materials, such as casein, animal glue, methyl cellulose, and gum tragacanth, are representative of the class of substances which are useful. When employed in the proper proportions, these materials bond the solid particles in the lubricant coating and cause the coating to adhere to the slug. Also, these substances within the proportions given below have the property of not forming an objectionable carbonaceous film during the drying and slug preheating operations as do oils and greases. The adhesive materials may be used separately or two or more may be employed simultaneously in a given mixture. Of the various adhesives, we prefer casein. Numerous water paint powders contain substantial amounts of casein in addition to other materials, and the casein for the slurry described herein can be supplied conveniently by means of such paint powders.

The third component of the lubricant mixture should be an inorganic soluble salt that is dissolved in the vehicle, such as sodium chloride, calcium chloride, sodium sulfate, or the like, and which is stable at the hot working temperatures. The term stable means that the salt does not vaporize or decompose to any marked extent at these temperatures. Some salts, .however, such as magnesium sulfate, have been found to be incompatible with casein, causing it to curdle. In general, any substance which is not compatible with the adhesive, that is, which causes it to agglomerate or reacts with it to form an insoluble compound is to be avoided and conversely those inorganic salts recognized in field of colloids which do not produce agglomeration can be used if they do not vaporize or decompose to any substantial degree during the slug preheating and hot working operations. The three components specified above are necessary to obtain superiority in appearance of the shaped article, fill rating, accuracy of dimensions, and flow of metal into the die recesses as compared to the behavior of any one or two of the components.

The total quantity of lubricant, adhesive and salt in the slurry applied to the slug should range between about and per cent by weight of the total weight of the mixture. If less than 10 per cent is used, the lubricant coating is insufficient to provide the necessary lubrication, while more than about 30 per cent produces too heavy a coating that flakes off or prevents proper filling of the dies or produces a rough surface on the forging or pressing. Within this range the graphite or similar lubricant should amount to 3 to 20 per cent of the total weight of the slurry, the adhesive should constitute from about 0.25 to 4 per cent of the total weight, and the salt com-'- ponent may range from 1.5 to 20 per cent of the total. If some inert materials are associated with the desired components, they should not be present in amounts sufficient to produce too thick a slurry, it being desirable that the slurry be rela tively thin to avoid producing a coating which flakes off or prevents proper filling of the dies.

The preferred lubricant slurry consists of casein paint powder, sodium chloride, lubricating grade of graphite, and water. When mixed with water, the pure casein should represent about 0.25 to 4 per cent of the total Weight, the graphite from 3 to 20 per cent, and the salt from about 1.5 to 20 per cent. To produce a successful lubricant coating, the minimum amounts of each of the three foregoing components should not be employed simultaneously. The smallest quantity of each that should be used under such conditions is 7.5 per cent of graphite, 0.8 per cent of casein, and 1.7 per cent of sodium chloride. A preferred range for each of the three components mentioned above is 0.4 to 1.6 per cent casein, 3 to 7 per cent sodium chloride, and 8 to 16 per cent graphite.

Under some circumstances it has been found to be advisable to add a relatively small amount of one or more substances'which tend to stabilize the slurry, that is, to minimize any tendency of the components to settle to the bottom of the container. One such substance is gelatin glue that may be employed within a range of about 0.1 to 0.5 per cent by weight. Although these substances may serve as an adhesive, their primary function is that of improving the quality of the lubricant in the slurry stage.

It is convenient to apply the slurry by immersing the slugs in it prior to their being heated to the working temperature. A particularly ad vantageous procedure is to heat the slugs, prior to applying the slurry, to a temperature sufficient to cause the vehicle of the slurry to volatilize rapidly when the slurry is applied, so that the operations of applying the slurry and driving off the vehicle are combined. With that procedure the slug to be coated should be at a temperature between about 200-500 F. At higher temperatures an unsatisfactory and non-uniform coating is formed while at lower temperatures evaporation is too slow and the coating is not sufficiently adherent immediately after application of the slurry. It is desirable that the slugs be cleaned prior to application of the slurry to them. In the case of aluminous metal products a caustic dip will suifice for this purpose.

The coating may be applied to the slugs in various manners, but either dipping the hot slug or spraying it are the easiest procedures. The coating operation may be performed just before the metal working operation, if the temperature of the slug does not exceed 500 F. However, in most working operations the working temperature is much higher, and therefore the lubricant should be applied before the slug is heated to the working temperature.

The organic adhesive does not appear to carbonize during drying or preheating operations or if it does, to some extent, the adhesive property remains, for the lubricant coating adheres well to the slugs.

Following the final working operation, the shaped articles should be immersed in water or otherwise cleaned to remove any remaining traces of lubricant. The adhesive and the salt compsw nent's either dissolve in or are readily loosened from the slug by water which also serves to dislodge the graphite. The coating is therefore much more easily removed than is the common carbonized oil-graphite film.

Although the lubricant described above is use ful in the working of many metal articles, we have found that it has particular advantage in the working of aluminous metal products. The lubricant is well adapted for use in a system where the slugs are heated in a continuous conveyor type of furnace to a temperature, for example, between 800 and 950 F., the slugs being dipped in the lubricant before being placed on the conveyor.

The above described lubricant is useful in different hot working operations of the forging type. It can be employed in making the customary hammer forgings where the metal is shaped under a sudden impact, or it may be used in press forging operations where the pressure is applied to the slug more gradually. In general, the lubricant is applicable to the hot shaping of slugs between dies, but the best results have been obtained in press forging operations. The lubricant has been found to be especially suitable in making aluminous metal press forgings within a temperature range of about 700 to 850 F.

in employing the lubricant coating described herein, it may be desirable to supplement it by occasionally spraying the dies with conventional lubricants; however, this is a matter of choice dictated by the particular type of article being shaped.

It has been found in plant operations that through the use of the dried lubricant coating described, the smoke nuisance has been completely eliminated. It has also been observed that the articles fill the dies better and the need for the conventional vents is eliminated. Furthermore, it is easy to remove any lubricant residue from the article by immersing it in water, which provides considerable advantage over the oilgraphite type of lubricant under the same conditions.

Having thus described our invention, we claim:

1. A slurry for application to slugs to be forged or pressed consisting essentially of water, from about 3 to 20 per cent of finely divided solid undissolved mineral lubricating material which is stable at the forging or pressing temperature to which the slugs are subjected, from about 0.25 to 4 per cent of an organic adhesive uniformly distributed throughout the slurry which is soluble in water or capable of forming a colloid or suspension therein and which does not form a carbonaceous film during the drying and preheating operations preparatory to forging or pressing, and from 1.5 to 20 per cent of a compatible inorganic wateresoluble salt inert toward said adhesive and stable at the forging or pressing temperature, the total amount of said lubricating material, organic adhesive and salt constituting from to 30 per cent by weight of the slurry.

2. A slurry for application to slugs to be forged or pressed consistin essentially of water, not less than 3 per cent of finely divided solid undissolved mineral lubricating material which is stable at the forging or pressing temperature to which said slugs are subjected, 0.25 to 4 per cent of'an organic adhesive uniformly distributed throughout the slurry which is soluble in water or capable of forming a colloid or suspension therein and which does not form a carbonaceous film during the drying and preheating operations preparatory to forging or pressing and not. less than 1.5 per cent of a compatible inorganic water-soluble salt inert toward said adhesive and stable at the forging or pressing temperature, the total amount of said lubricating material, organic adhesive and salt constituting from 10 to 30 per cent by weight of the slurry.

3. A slurry for application to metal slugs to be forged or pressed consisting essentially of water, from 3 to per cent by weight of a flake-like lubricating material selected from the group consisting of graphite, mica and aluminum powder, from 0.25 to 4 per cent of an organic adhesive uniformly distributed throughout the slurry which is soluble in water or capable of forming colloid or suspension therein and which does not form a carbonaceous film during the drying and preheating operations preparatory to forging or pressing, and from 1.5 to 20 per cent of a compatible inorganic water-soluble salt inert toward said adhesive and stable at the forging or pressing temperature, the total amount of said lubricating material, organic adhesive and salt constitutin from 10 to per cent by weight of the slurry.

4. A slurry for application to slugs to be forged or pressed consisting essentially of water, from about 3 to 20 per cent graphite, 0.25 to 4 per cent casein, and about 1.5 to :20 per cent sodium chloride, total amount of said graphite, casein and sodium chloride together constituting from 10 to 30 per cent by weight of the slurry.

5. A slurry for application to slugs to be forged or pressed consisting essentially of water, from about 8 to 16 per cent graphite, 0.4 to 1.6 per cent casein and 3 to 7 per cent sodium chloride.

\ 6. A slurry for application to slugs to be forged or pressed consisting essentially of water, from about 3 to 20 per cent mica, 0.25 to 4 per cent casein and 1.5 to 20 per cent sodium chloride, the total amount of said mica, casein and sodium chloride together constituting about 10 to 30 per cent by weight of the slurry.

'7. A slurry for application to slugs to be forged or pressed consisting essentially of water, from about 3 to 20 per cent of aluminum powder, 0.25 to 4 per cent casein, and 1.5 to 20 per cent sodium chloride, the total amount of said aluminum powder, casein and sodium chloride together constituting from 10 to 30 per cent by weight of the slurry.

I 8. In the art of forging or pressing metal slugs, the method of lubricating said slugs comprising heating them to a temperature between 200 and 500 F., coating them with a slurry prior to hot working, said slurry consisting essentially of water, not less than 3 per cent by weight of finely divided solid undissolved mineral lubricating material which is stable at the hot working temperature to which said slugs are to be subjected, 0.25 to 4 per cent by weight of an organic adhesive uniformly distributed throughout the slurry whichis soluble in water or capable of forming a colloid or suspension therein and which does not form the carbonaceous film during the drying and preheating operations preparatory to hot working, and not less than 1.5 per cent by weight of a compatible inorganic watersoluble salt inert toward said adhesive and stable at the hot working temperature, the total amount of said lubricating material, organic adhesive and salt constituting from 10 to 30 per cent by weight of said slurry, maintaining said slugs within the temperature range of 200 to 500 F. to vaporize said water and leave a solid adherent coating of said lubricating material, adhesive and salt.

9. In the art of forging or pressing metal slugs, the method of lubricating said slugs comprising heating them to a temperature between 200 and 500 F., immersin them in a slurry prior to hot working, said slurry consisting essentially of water, not less than 3 per cent by weight of finely divided solid undissolved mineral lubricating material which is stable at the hot working temperature to which said slugs are subjected, 0.25 to 4 per cent by weight of an organic adhesive uniformly distributed throughout the slurry which is soluble in water or capable of forming a colloid or suspension therein and which does not form a carbonaceous film during the drying and preheating operations preparatory to hot working, and not less than 1.5 per cent by weight of a compatible inorganic water-soluble salt inert toward said adhesive and stable at the hot working temperature, the total amount of said lubricating material, organic adhesive and salt constituting from 10 to 30 per cent by weight of said slurry, withdrawing said hot slugs from said slurry, maintaining said coated slugs at a temperature between 200 and 500 F. to allow the water to vaporize and leave a solid adherent coating of said lubricating material, adhesive and salt.

10. In the art of forging or pressing aluminous metal slugs, the method of lubricating said slugs comprising heating them to a temperature between 200 and 500 F., coating them with a slurry prior to hot working, said slurry consisting essentiall of water, not less than 3 per cent by weight of finely divided solid undissolved mineral lubrieating material which is stable at the hot working temperature to which said slugs are subjected, 0.25 to 4 per cent by weight of an organic adhesive uniformly distributed throughout the slurry which is soluble in water or capable of forming a colloid or suspension therein and which does not form a carbonaceous film durin the drying and preheating operations preparatory to hot working and not less than 1.5 per cent by weight of a compatible inorganic water-soluble salt inert toward said adhesive and stable at the hot working temperature, the total amount of said lubricatin material, organic adhesive and salt constituting from to 30 per cent by weight of said slurry, maintaining said coated slugs at a temperature between 200 and 500 F. to rapidly vaporize said water and leave a solid adherent coating of said lubricating material, adhesive and salt.

11. In the art of forging or pressing metal slugs, the method of lubricating said slugs comprising heating them to a temperature between 200 and 500 F., coating them with a slurr prior to hot working, said slurry consisting essentially of water,from 3 to per cent by weight of finely divided solid undissolved mineral lubricating material which is stable at the hot working temperature to which the slugs are subjected, 0.25 to 4 per cent by weight of an organic adhesive uniformly distributed throughout the slurry which is soluble in water or capable of forming a colloid or suspension therein and which does not form a carbonaceous film during the drying and preheating operations preparatory to hot working, and from 1.5 to 20 per cent by weight of a compatible dissolved inorganic salt inert toward said adhesive and stable at the hot working temperature, the total amount of said lubricating material, organic adhesive and salt constituting from 10 to 30 per cent by weight of said slurry, and maintaining said slugs within the temperature range of 200 to 500 F. to vaporize said water and leave a solid adherent coating of said lubricant, adhesive and salt.

12. In the art of forging or pressing metal slugs, the method of lubricating said slugs comprising heating them to a temperature between 200 and 500 F., coating said slugs with a slurry prior to hot working, said slurry consisting essentially of water, from 3 to 20 per cent by weight of a flake-like lubricating substance selected from the group consisting of graphite, mica and aluminum powder, 0.25 to 4 per cent by weight of an organic adhesive uniformly distributed throughout the slurry which is soluble 8 in water or capable of forming a colloid or suspension therein and which does not form a carbonaceous film during the drying and preheating operations preparatory to hot working, and 1.5 to 20 per cent by weight of a compatible dissolved inorganic salt inert toward said adhesive and stable at the hot working temperature, the total amount of said lubricating material, organic adhesive and salt constituting 10 to 30 per cent by weight of said slurry, and maintaining said slugs within the temperature range of 200 to 500 F. to vaporize said water and leave a solid adherent coating of said lubricant, adhesive and salt.

13. In the art of pressing and forging aluminous metal slugs, the method of lubricating said slugs comprising heating them to a temperature between 200 and 500 F., immersing them in a slurry prior to hot working, said slurry consisting essentially of water, 3 to 20 per cent by weight of graphite, 0.25 to 4 percent by weight of casein, and 1.5 to 20 percent by weight of sodium chloride, the total amount of said graphite, casein and sodium chloride constituting 10 to 30 percent by weight of said slurry, withdrawing said slugs from the slurry, maintaining said slugs within a temperature range of 200 to 500 F. to allow said water to vaporize and leave a coating of graphite, casein and sodium chloride.

WARREN E. FERNER. GEORGE ALEXANDER. JOHN ROBINSON. WALTER E. STREETER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 237,437 Hurty Feb. 8, 1881 310,827 Hungate Jan. 13, 1885 416,100 Freist Nov. 26, 1889 1,226,165 Axtell May 15, 1917 1,249,249 Thorswik Dec. 4, 1917 1,409,658 Brann Mar. 14, 1922 1,410,967 Thompson Mar. 28, 1922 1,780,566 Pederson Nov. 4, 1930 1,946,121 Wood Feb. 6, 1934 1,952,973 Craig Mar. 27, 1934 2,126,128 Montgomery Aug. 9, 1933 2,132,243 Menaker Oct. 4, 1938 2,169,444 Dahlberg Aug. 15, 1939 2,196,128 Stuart Apr. 2, 1940 2,258,309 Zimmer Oct. 7, 1941 2,430,092 Westin Nov. 4, 1947 OTHER REFERENCES Colloidal Graphite-A Modern Lubricant, vol. 52, part 1, pp. 50-52, Chem. Ind. January 1943. 

1. A SLURRY FOR APPLICATION TO SLUGS TO BE FORGED OR PRESSED CONSISTING ESSENTIALLY OF WATER, FROM ABOUT 3 TO 20 PER CENT OF FINELY DIVIDED SOLID UNDISSOLVED MINERAL LUBRICATING MATERIAL WHICH IS STABLE AT THE FORGING OR PRESSING TEMPERATURE TO WHICH THE SLUGS ARE SUBJECTED, FROM ABOUT 0.25 TO 4 PER CENT OF AN ORGANIC ADHESIVE UNIFORMLY DISTRIBUTED THROUGHOUT THE SLURRY WHICH IS SOLUBLE IN WATER OR CAPABLE OF FORMING A COLLOID OR SUSPENSION THEREIN AND WHICH DOES NOT FORM A CARBONACEOUS FILM DURING THE DRYING AND PREHEATING OPERATIONS PREPARATORY TO FORGING OR PRESSING, AND FROM 1.5 TO 20 PER CENT OF A COMPATIBLE INORGANIC WATER-SOLUBLE SALT INERT TOWARD SAID ADHESIVE AND STABLE AT THE FORGING OR PRESSING TEMPERATURE, THE TOTAL AMOUNT OF SAID LUBRICATING MATERIAL, ORGANIC ADHESIVE AND SALT CONSTITUTING FROM 10 TO 30 PER CENT BY WEIGHT OF THE SLURRY.
 8. IN THE ART OF FORGING OR PRESSING METAL SLUGS, THE METHOD OF LUBRICATING SAID SLUGS COMPRISING HEATING THEM TO A TEMPERATURE BETWEEN 200 AND 500* F., COATING THEM WITH A SLURRY PRIOR TO HOT WORKING, SAID SLURRY CONSISTING ESSENTIALLY OF WATER, NOT LESS THAN 3 PER CENT BY WEIGHT OF FINELY DIVIDED SOLID UNDISSOLVED MINERAL LUBRICATING MATERIAL WHICH IS STABLE AT THE HOT WORKING TEMPERATURE TO WHICH SAID SLUGS ARE TO BE SUBJECTED, 0.25 TO 4 PER CENT BY WEIGHT OF AN ORGANIC ADHESIVE UNIFORMLY DISTRIBUTED THROUGHOUT THE SLURRY WHICH IS SOLUBLE IN WATER OR CAPABLE OF FORMING A COLLOID OR SUSPENSION THEREIN AND WHICH DOES NOT FORM THE CARBONACEOUS FILM DURING THE DRYING AND PREHEATING OPERATIONS PREPARATORY TO HOT WORKING, AND NOT LESS THAN 1.5 PER CENT BY WEIGHT OF A COMPATIBLE INORGANIC WATERSOLUBLE SALT INERT TOWARD SAID ADHESIVE AND STABLE AT THE HOT WORKING TEMPERATURE, THE TOTAL AMOUNT OF SAID LUBRICATING MATERIAL, ORGANIC ADHESIVE AND SALT CONSTITUTING FROM 10 TO 30 PER CENT BY WEIGHT OF SAID SLURRY, MAINTAINING SAID SLUGS WITHIN THE TEMPERATURE RANGE OF 200 TO 500* F. TO VAPORIZE SAID WATER AND LEAVE A SOLID ADHERENT COATING OF SAID LUBRICATING MATERIAL, ADHESIVE AND SALT. 